2000 Focus ZTS 2.0 DOHC
Fresh tune-up (wires and plugs), air filter, fuel filter, coil pack, MAF cleaned with MAF cleaner. No vacuum leaks that I can find. But until it warms up its very slow. Just lacks power. No codes registered yet. So what could possibly cause this? Bad temp sensor? Or another sensor? Any help is appreciated. Thanks!

What vacuum lines are operating when its cold, but not hot? Because the brakes feel stiff at the same time this happens.

Um.. you only have one vac line controlled by a solenoid, and that's the purge line from the EVAP system. All vacuum lines should be operating all the time. Have you inspected the lines?

Do not be afraid, there are not many- like 4-5. Follow the VECI diagram under the hood. You might also have a problem with your check valve on the power brake booster or the booster itself.

I'd check the usual vacuum issue suspect: the PCV vacuum line. Of course it's important to check all of the lines for damage, but this one is the one that seems to cause the most problems.

Also, an engine that is running on like 2 cyls will have a hard brake pedal because it isn't producing vacuum like a normal engine, so that issue could be another symptom of your engine issue instead of a cause.

Um.. you only have one vac line controlled by a solenoid, and that's the purge line from the EVAP system. All vacuum lines should be operating all the time. Have you inspected the lines?

Do not be afraid, there are not many- like 4-5. Follow the VECI diagram under the hood. You might also have a problem with your check valve on the power brake booster or the booster itself.

I'd check the usual vacuum issue suspect: the PCV vacuum line. Of course it's important to check all of the lines for damage, but this one is the one that seems to cause the most problems.

Also, an engine that is running on like 2 cyls will have a hard brake pedal because it isn't producing vacuum like a normal engine, so that issue could be another symptom of your engine issue instead of a cause.

Its running on all four cylinders now. I have traced the vacuum lines and used intake cleaner spray to verify that there are not any leaks. The brake booster or valve could be culprit still. But after it warms a little they operate fine. Or when I rev the motor over 2k in neutral within a minute of starting it cold in the morning. My thoughts are that it could be the temp sensor. When it runs open loop it uses this to calculate the fuel mix. Also I dont know when the O2 sensor was changed if ever. So that is on the list of things to do next as well. But the O2 sensor would only affect closed loop driving.

Okay, so here's the million dollar question and something I dont fully understand. On the intake there are four ports. From the passenger side to the drivers side all vacuum lines are accounted for save one. The port on the far right (drivers side looking from the front of the car). Its not the brake booster port and the vacuum diagram is clear as mud. But I think its suppose to connect to the "VMV" . What does that stand for and where is it located on the car. I have a feeling its causing my problems. I have the vacuum port capped at this point and time so its not causing a leak. But this is driving me nuts!

cars are sluggish when the engine is cold. u should not rev it or have the RPMs go high before it gets warmed up. its bad for the engine. when cold, the oil is thicker and its hard to run through the engine.

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